1. Field of the Invention
The present invention relates to the field of integrated processors executing a program or any data manipulation to provide a result.
The present invention more specifically relates to the detection of an error (voluntary or incidental) in the program execution. Such errors or faults may result from the occurrence of a temporary current on the processor power supply for a short time (known as a glitch), from a variation in the processor power supply voltage or a program trap attempt by any other means.
2. Discussion of the Related Art
The detection of a possible fault injection in the execution of a program by an integrated processor is used, for example, to detect a possible modification in the sequencing of the program instruction series. Such a modification may be part of an attack aiming at discovering secret data manipulated by a program algorithm. For example, in an authentication, authorization or the like process, certain branching are critical. If the program is trapped by being forced to execute one or several instructions, this may lead to a violation of the authentication procedure.
A first conventional example of a fault detection system consists of controlling the program execution by calculating an execution signature and checking this signature against a pre-recorded signature. A disadvantage of such a technique is that it is only applicable to pre-established data, and thus on a portion of the code itself and cannot take account of the processed data. Another disadvantage is that the control can only be performed a posterior, at the end of the program execution.
A second known technique consists of executing a program more than once (redundancy), and only validating a result if these executions each time provide the same result. A disadvantage of such a technique is that it requires significant hardware and/or software resources which further are a function of the complexity of the program which is desired to be monitored. Moreover, permanent errors (permanent forcing of a given state) are not detected.